On certain architectures such as x86 the bootstrap processor
does most of the work. When CACHE_ROM is employed it's appropriate
to ensure that the caching enablement of the ROM is disabled so that
the caching settings are symmetric before booting the payload or OS.

Tested this on an x86 machine that turned on ROM caching. Linux did not
complain about asymmetric MTRR settings nor did the ROM show up as
cached in the MTRR settings.